Introduction
Epicardial pacemakers are known as an alternative for endocardial pacemakers not only for newborns with bradycardia due to sinus node disease or heart block but also in pediatrics and adults with complex congenital heart diseases. Regarding newborns and children, rapid somatic growth, small vessel size, and lack of access to the chamber requiring pacing make it hard to implement endocardial pacemakers; therefore, in these cases, permanent epicardial pacemakers are the first priority. Moreover, congenital heart disease with right-to-left shunts and intention to preserve venous access and prevent venous thrombosis (often in pediatric patients) are among other reasons to prefer epicardial pacemakers.1,2
Endocardial pacemakers showed better longevity than epicardial leads with higher failure over time mainly due to high thresholds, exit blocks, and fractures of epicardial leads.3Endocardial pacemakers are implemented in the right side of the heart and lateral wall of the left ventricle through the coronary sinus, which is not applicable in 4.3 to 7.5 % of cases due to abnormal venous anatomy.4,5 Furthermore, studies indicated that long-term endocardial pacemakers could result in impaired LV function.6 Otherwise, epicardial leads are directly applicable on the left ventricle and might be a more appropriate choice for patients with RV dysfunction.7
Advances in epicardial pacemakers in recent decades resulted in improvement in the long-term function of these leads. Currently, these pacemakers have different characteristics, such as being unipolar or bipolar and steroid-eluting or non-steroid-eluting. Previous studies demonstrated that steroid-eluting epicardial leads have a comparative stable pacing threshold.1,8 For instance, a 12-year follow-up of the children with bipolar steroid-eluting leads illustrated outstanding sensing characteristics and low median pacing threshold, making them an appropriate alternative for permanent endocardial pacemakers.2
Considering the abovementioned indication for epicardial pacemakers, recent advances, and their various characteristics, it is essential to evaluate and compare the long-term function of each subtype. In this study, we aimed to assess the sensing and pacing characteristics, and survival of different types of epicardial pacemakers and their associated factors through a 4-year follow-up of all patients who underwent epicardial pacemaker implantation in the Shaheed Rajaie Cardiovascular, Medical & Research Center.